Ubuntu environment variables and ADB configuration

Ubuntu Linux environment variables

Like Windows, the Ubuntu Linux system contains two types of environment variables: system environment variables and user environment variables. System environment variables are valid for all system users, and user environment variables are only valid for the current user.

User environment variables are usually stored in the following files:

• ~ /.profile
• ~ /.bash_profile or ~./bash_login
• ~ /.bashrc

The above files are not recommended for use in versions prior to Ubuntu 10.0.

System environment variables are generally stored in the following files:

• /etc/environment
• /etc/profile
• /etc/bash.bashrc

/etc/profile and /etc/bash.bashrc are not recommended in Ubuntu 10.0 version.

Priority of Ubuntu Linux environment variables

1. /etc/profile: When logging in, the first file used by the operating system to customize the user environment. This file sets environment information for each user of the system. This file is automatically executed when the user logs in for the first time.
2. /etc/environment: The second file used by the operating system when logging in. The system sets the environment variables of the environment file before reading your own profile.
3. ~ /.bash_profile: The third file used when logging in is the .profile file. Each user can use this file to enter shell information dedicated to his own use. When the user logs in, the file is executed only once! By default , He sets up some environment variables and executes the user's .bashrc file. /etc/bashrc: This file is executed for each user who runs the bash shell. When the bash shell is opened, the file is read.
4. ~ /.bashrc: This file contains bash information dedicated to your bash shell. This file is read when you log in and every time you open a new shell.
5. /etc/bash.bashrc: A script that is automatically executed when the user enters the shell or desktop system

The priority of several environment variables: 1>2>3

Set adb environment variables in Ubuntu Linux

• Current user (homer)

vi ~/.bashrc (The bashrc file in the root default directory)

Add in this file: export PATH=/home/homer/android-sdk-linux/platform-tools/:$PATH

It takes effect after restarting or logging in again. If you want to take effect immediately, execute: source ~/.bashrc

• Super User (root)

su root

vi ~/.bashrc (The bashrc file in the root default directory)

Add in this file: export PATH=/home/homer/android-sdk-linux/platform-tools/:$PATH

It takes effect after restarting or logging in again. If you want to take effect immediately, execute: source ~/.bashrc

• Global settings (homer, root, sudo)

**1. **Realization ideas:

Create a soft link for adb in the default bin directory of PATH

**2. **View sudo $PATH: echo'echo $PATH' | sudo sh

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin

**3. **Enter sudo default PATH:

cd /usr/local/bin/

**4. **Establish soft link:

sudo ln -s /home/homer/android-sdk-linux/platform-tools/adb

**5. **In this way, in ordinary users (homer), super users (root), and sudo users, you can directly use the adb command, because the PATH environment variable of these users includes the directory /usr/local/bin

Ubuntu Linux cannot recognize the phone

homer@ubuntu:~$ adb devices
List of devices attached 
???????????? no permissions

Ubuntu Linux starts phone recognition

homer@ubuntu:~$ sudo adb kill-server
homer@ubuntu:~$ sudo adb start-server

• daemon not running. starting it now on port 5037 *
• daemon started successfully *
  homer@ubuntu:~$ adb devices
  List of devices attached 
  FM6111131707 device

Reference recommendation:

The execution process of several files such as /etc/profile, ~/.bash_profile in Linux

Several ways and differences of setting environment variables in Ubuntu

Android real machine debugging garbled (no mobile phone recognition)